Adjustable polarizer for head up displays

ABSTRACT

A head up display arrangement for a motor vehicle includes a head up display module having a picture generation unit emitting a light field. A polarizing device is rotatable between at least a first rotational position and a second rotational position. The polarizing device receives the light field from the picture generation unit and emits the light field regardless of whether the polarizing device is in the first rotational position or the second rotational position. More of the light is emitted by the polarizer in a P-polarization state in the second rotational position than in the first rotational position. A windshield reflects the light field from the polarizing device such that the reflected light field is visible to a human driver of the motor vehicle as a virtual image.

CROSS-REFERENCED TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/502,865, filed on Jul. 3, 2019, which is currently under allowance,which claims benefit of U.S. Provisional Application No. 62/694,335filed on Jul. 5, 2018, the disclosure of which are hereby incorporatedby reference in their its entirety for all purposes.

FIELD OF THE INVENTION

The disclosure relates to a head up display (HUD) in a motor vehicle.

BACKGROUND OF THE INVENTION

A head up display emits light that reflects from the front windshield tobe seen by the driver. The light appears to come from a virtual image infront of the driver and in front of the windshield. This type of head updisplay is currently commercially available.

Conventional head up displays create the virtual image by first using adisplay to create an image. Next, the light from the image is reflectedfrom one or more mirrors. Next, the light from the mirrors is reflectedfrom the windshield. The mirrors are designed and positioned relative tothe display so that the light seen by the driver, which is reflectedfrom the windshield, appears to come from a virtual image that isoutside of the vehicle. The mirrors and display are typically containedin a package that occupies a volume beneath the top surface of thedashboard.

Many current owners of HUD-equipped vehicles have expressed unhappinesswith inability to view the HUD image while wearing polarized sunglasses.The following methods are known to enable the image of a windshield HUDto be viewed with polarized sunglasses: (1) The HUD projector emitscircularly polarized or elliptically polarized light. This is not afully satisfactory solution since the windshield reflectivity top-polarized light is small; (2) The driver can wear non-polarizingsunglasses; (3) A plastic lens, including a wave plate, can be clippedover the polarizing sunglasses; and (4) An interior surface of thewindshield can be coated with a reflective layer. Doing so increaseswindshield reflectance, and, as a result, increases veiling glare.

Currently, virtual images produced by head up displays become extremelydim when the user is wearing polarized sunglasses. In some instances,the virtual image completely disappears because the light coming towardsthe driver has a majority of its light in one polarization state.

There is no known solution to the problem of a dim virtual image. Adriver wearing polarized sunglasses cannot see the virtual imageproduced by the HUD on a sunny day.

Circularly polarizing the light after the picture generation unit (PGU)may help slightly, but it does not solve the problem.

SUMMARY

The present invention may provide a head up display (HUD) system thatreflects light from the front windshield of a vehicle to be seen by thedriver as a virtual image. In one embodiment, the system includes anadditional optical element which enables the driver to see the virtualimage when he is wearing polarized sunglasses. A rotatable polarizingdevice may be disposed in front of the liquid crystal display (LCD), andmay rotate over an angular distance which results in the light shiftingto either P-polarized light or S-polarized light. The driver may depressa “Polarized Sunglasses” button which causes the polarizing device torotate, and the image may thus become brighter through polarizedsunglasses. The rotation of the polarizing device may enable the lightto pass through the polarized sunglasses, making the image much brighterand visible to the user.

In one embodiment, the invention comprises a head up display arrangementfor a motor vehicle, including a head up display module having a picturegeneration unit emitting a light field. A polarizing device is rotatablebetween at least a first rotational position and a second rotationalposition. The polarizing device receives the light field from thepicture generation unit and emits the light field regardless of whetherthe polarizing device is in the first rotational position or the secondrotational position. More of the light is emitted by the polarizingdevice in a P-polarization state in the second rotational position thanin the first rotational position. A windshield reflects the light fieldfrom the polarizing device such that the reflected light field isvisible to a human driver of the motor vehicle as a virtual image.

In another embodiment, the invention comprises a head up display method,including providing a head up display module including a picturegeneration unit and a polarizing device. Light is emitted by use of thepicture generation unit. Light from the picture generation unit ispassed through the polarizing device while the polarizing device is in afirst rotational position. A first fraction of the light is in aP-polarization state after passing through the polarizing device in thefirst rotational position. The polarizing device is rotated from thefirst rotational position to a second rotational position. Light fromthe picture generation unit is passed through the polarizing devicewhile the polarizing device is in a second rotational position. A secondfraction of the light is in a P-polarization state after passing throughthe polarizing device in the second rotational position. The secondfraction is greater than the first fraction. Light that has passedthrough the polarizing device is reflected off of a windshield such thatthe reflected light field is visible to a human driver of a motorvehicle as a virtual image.

In yet another embodiment, the invention comprises a head up displayarrangement for a motor vehicle, including a user interface and a headup display module having a picture generation unit emitting a lightfield. A polarizing device is rotatable between at least a firstrotational position and a second rotational position. The polarizingdevice passes the light field from the picture generation unit in boththe first rotational position and the second rotational position. Agreater percentage of the light is passed by the polarizing device in aP-polarization state in the second rotational position than in the firstrotational position. At least one movable mirror reflects the lightfield from the polarizing device. A motor is selectively couplable tothe polarizing device and to the at least one movable mirror such thatthe motor may rotate the polarizing device and move the at least onemovable mirror. An electronic processor is communicatively coupled tothe user interface and to the motor. The electronic processor respondsto a first signal from the user interface by causing the motor to movethe at least one movable mirror. The electronic processor responds to asecond signal from the user interface by causing the motor to rotate thepolarizing device. A windshield reflects the light field from the atleast one movable mirror such that the reflected light field is visibleto a human driver of the motor vehicle as a virtual image.

An advantage of the present invention is that it solves the problem ofthe driver not being able to see the HUD virtual image while wearingordinary polarizing sunglasses.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention will be had uponreference to the following description in conjunction with theaccompanying drawings.

FIG. 1 is a schematic side view of one embodiment of an automotive headup display arrangement of the present invention.

FIG. 2 is a plan view of one embodiment of a set of driver HUD controlsof the present invention.

FIG. 3 is a flow chart of one embodiment of an automotive head updisplay method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates one embodiment of an automotive head up displayarrangement 10 of the present invention, including a HUD module 12 and awindshield 14. HUD module 12 includes a PGU 16, a rotatable polarizingdevice 18, a first mirror 20, and a second mirror 22. Polarizing device18 may be rotatable within a span of 90 degrees about an axis 24 inorder to provide more P-polarized light when rotated toward one end ofthe span, or less P-polarized light when rotated to the other, oppositeend of the span. Polarizing device 18 may be in the form of a polarizer,a ¼ wave plate, or a ½ wave plate.

Polarizing device 18 may be rotated through its range of motion by amotor 26. It is also possible for motor 26 to be used as the HUD'sstepper motor.

A light field 27 coming from PGU 16 may be generally polarized bypolarizing device 18 all in either P- or S-polarization state. Most ofthe P-polarized light is lost at windshield 14, and the P-polarizationstate is the polarization state that is able to get through thepolarized sunglasses. By using polarizing device 18 to provide a greaterpercentage of the energy in the P-polarized state, more brightness maybe achieved at the eye in the P-polarized state.

FIG. 2 illustrates one embodiment of a set of driver HUD controls of thepresent invention, which may be on a center console or dashboard of themotor vehicle, for example. The HUD controls include a brightness toggleswitch 28, a vertical position toggle switch 30, an ON/OFF pushbutton32, and a “polarized sunglasses” pushbutton 34. A microprocessor 40 iscommunicatively coupled to each of switches 28, 30, and to each ofpushbuttons 32, 34. Microprocessor 40 may also be communicativelycoupled to PGU 16, motor 26, and a mechanical switch 42. Switch 42 mayselectively couple motor 26 to either polarizing device 18, first mirror20, or second mirror 22. Microprocessor 40 may control the position ofswitch 42, and thus may control whether motor 26 can actuate polarizingdevice 18, first mirror 20, or second mirror 22. As mentioned above,motor 26 may be in the form of a stepper motor in one embodiment.

During use, light 27 from PGU 16 may be polarized by polarizing device18, and reflected by mirrors 20, 22 and windshield 14 toward a user 36.Light 27 may appear to user 36 as a virtual image 38. If user 36 plansto wear polarized sunglasses, user 36 may select and depress polarizedsunglasses pushbutton 34, which may cause polarizing device 18 to rotateand thereby allow more of the P-polarized light to be reflected fromwindshield 14 and reach the eyes of user 36. Accordingly, a virtualimage 38 may be visible to user 36 even when wearing polarizedsunglasses.

If user 36 manually moves toggle switch 28 to either brighten or dimdown virtual image 38, switch 28 may transmit a signal to processor 40.Processor 40 may respond to this signal by causing PGU 16 to eitherproduce a brighter or dimmer light field 27.

If user 36 manually depresses pushbutton 32 to either turn ON or turnOFF virtual image 38, pushbutton 32 may transmit a signal to processor40. Processor 40 may respond to this signal by causing PGU 16 to eitherstart producing light field 27 or cease producing light field 27.

If user 36 manually moves toggle switch 30 to either raise or lowervirtual image 38, switch 30 may transmit a signal to processor 40.Processor 40 may respond to this signal by moving switch 42 to couplemotor 26 to mirror 20 and/or mirror 22. Processor 40 may then causemotor 26 to move mirror 20 and/or mirror 22 to make virtual image 38rise or fall, as desired by user 36.

If user 36 manually depresses pushbutton 34 when he puts on polarizedsunglasses to switch pushbutton 34 to the “ON” state, pushbutton 34 maytransmit a signal to processor 40. Pushbutton 34 may also light up toindicate that it is in an “ON” state to accommodate polarizedsunglasses. Processor 40 may respond to the signal from pushbutton 34 bymoving switch 42 to couple motor 26 to polarizing device 18. Processor40 may then cause motor 26 to rotate polarizer 18 such that the amountof P-polarized light that reaches user 36 is increased. Conversely, ifuser 36 manually depresses pushbutton 34 when he takes off polarizedsunglasses to switch pushbutton 34 to the “OFF” state, pushbutton 34 maytransmit a signal to processor 40. Processor 40 may respond to thesignal from pushbutton 34 by moving switch 42 to couple motor 26 topolarizer 18. Processor 40 may then cause motor 26 to rotate polarizingdevice 18 such that the amount of P-polarized light that reaches user 36is decreased.

FIG. 3 illustrates one embodiment of an automotive head up displaymethod 300 of the present invention. In a first step 302, a head updisplay module including a picture generation unit and a polarizingdevice is provided. For example, HUD module 12 includes a PGU 16 and arotatable polarizing device 18.

Next, in step 304, light is emitted by use of the picture generationunit. For example, light field 27 is emitted by PGU 16.

In a next step 306, light is passed from the picture generation unitthrough the polarizing device while the polarizing device is in a firstrotational position. A first fraction of the light is in aP-polarization state after passing through the polarizing device in thefirst rotational position. For example, polarizer 18 may be in a firstrotational position such that the amount of P-polarized light thatreaches user 36 is relatively low.

In step 308, the polarizing device is rotated from the first rotationalposition to a second rotational position. For example, processor 40 maycause motor 26 to rotate polarizer 18 from the first rotational positionto a second rotational position.

Next, in step 310, light is passed from the picture generation unitthrough the polarizing device while the polarizing device is in a secondrotational position. A second fraction of the light is in aP-polarization state after passing through the polarizer in the secondrotational position. The second fraction is greater than the firstfraction. For example, while polarizer 18 is in the second rotationalposition, the amount of P-polarized light that reaches user 36 isrelatively high, and greater than while polarizer 18 is in the firstrotational position.

In a final step 312, light that has passed through the polarizing deviceis reflected off of a windshield such that the reflected light field isvisible to a human driver of a motor vehicle as a virtual image. Forexample, light that has passed through polarizing device 18 may bereflected from windshield 14 such that the light appears to user 36 as avirtual image 38.

The foregoing description may refer to “motor vehicle”, “automobile”,“automotive”, or similar expressions. It is to be understood that theseterms are not intended to limit the invention to any particular type oftransportation vehicle. Rather, the invention may be applied to any typeof transportation vehicle whether traveling by air, water, or ground,such as airplanes, boats, etc.

The foregoing detailed description is given primarily for clearness ofunderstanding and no unnecessary limitations are to be understoodtherefrom for modifications can be made by those skilled in the art uponreading this disclosure and may be made without departing from thespirit of the invention.

What is claimed is:
 1. A head up display arrangement for a motorvehicle, comprising: a head up display module including: a picturegeneration unit configured to emit a light field; and a polarizingdevice that is movable between at least a first position and a secondposition, the polarizing device being configured to receive the lightfield from the picture generation unit and emit the light fieldregardless of whether the polarizing device is in the first position orthe second position, more of the light being emitted by the polarizingdevice in a P-polarization state in the second position than in thefirst position; and a windshield configured to reflect the light fieldfrom the polarizing device such that the reflected light field isvisible to a human driver of the motor vehicle as a virtual image. 2.The head up display arrangement of claim 1 wherein the first positionand the second position are rotationally about 90 degrees apart.
 3. Thehead up display arrangement of claim 1 wherein the polarizing device isrotatable about a substantially horizontal axis.
 4. The head up displayarrangement of claim 1 further comprising at least one mirror configuredto reflect the light field from the polarizing device onto thewindshield.
 5. The head up display arrangement of claim 4 furthercomprising a motor configured to move the polarizing device between thefirst position and the second position.
 6. The head up displayarrangement of claim 5 wherein the motor is configured to change anorientation of the at least one mirror.
 7. The head up displayarrangement of claim 6 wherein the motor is configured to be selectivelycoupled to either the polarizing device or the at least one mirror anddecoupled from the other one of the polarizing device and the at leastone mirror.
 8. A head up display module for a motor vehicle, comprising:a picture generation unit configured to emit a light field; and apolarizing device that is movable between at least a first position anda second position, the polarizing device being configured to receive thelight field from the picture generation unit and emit the light fieldregardless of whether the polarizing device is in the first position orthe second position, more of the light being emitted by the polarizingdevice in a P-polarization state in the second position than in thefirst position.
 9. The head up display module of claim 8 wherein thefirst position and the second position are rotationally about 90 degreesapart.
 10. The head up display module of claim 8 wherein the polarizingdevice is rotatable about a substantially horizontal axis.
 11. The headup display module of claim 8 further comprising at least one mirrorconfigured to reflect the light field from the polarizing device onto awindshield of the motor vehicle.
 12. The head up display module of claim11 further comprising a motor configured to move the polarizing devicebetween the first position and the second position.
 13. The head updisplay module of claim 12 wherein the motor is configured to change anorientation of the at least one mirror.
 14. The head up display moduleof claim 13 wherein the motor is configured to be coupled to the atleast one mirror.
 15. An automotive head up display module, comprising:a picture generation unit configured to emit light; a polarizing devicehaving a first position and a second position, the polarizing devicebeing configured to: pass therethrough a first fraction of the emittedlight that is in a P-polarization state while the polarizing device isin the first position; and pass therethrough a second fraction of theemitted light that is in a P-polarization state while the polarizingdevice is in the second position, the second fraction being greater thanthe first fraction.
 16. The module of claim 15 wherein the polarizingdevice is rotatable about 90 degrees between the first position and thesecond position.
 17. The module of claim 16 wherein the polarizingdevice is rotatable about a substantially horizontal axis between thefirst position and the second position.
 18. The module of claim 15further comprising at least one mirror configured to reflect the lightpassing through the polarizing device onto a windshield of a motorvehicle.
 19. The module of claim 18 further comprising a motorconfigured to move the polarizing device between the first position andthe second position.
 20. The module of claim 19 wherein the motor isconfigured to change an orientation of the at least one mirror.